This invention relates to electrostatographic reproduction machines, and more particularly to the charging and cleaning stations in an electrostatographic reproduction machine. Specifically this invention relates to such an electrostatographic reproduction machine including combined charging and cleaning.
Generally, the process of electrostatographic reproduction, as practiced in electrostatographic reproduction machines, includes charging a photoconductive member to a substantially uniform potential so as to sensitize the surface thereof. A charged portion of the photoconductive surface is exposed at an exposure station to a light image of an original document to be reproduced. Typically, an original document to be reproduced is placed in registration, either manually or by means of an automatic document handler, on a platen for such exposure.
Exposing an image of an original document as such at the exposure station records an electrostatic latent image of the original image onto the photoconductive member. The recorded latent image is subsequently developed using a development apparatus by bringing a charged dry or liquid developer material into contact with the latent image. Two component and single component developer materials are commonly used. A typical two-component dry developer material has magnetic carrier granules with fusible toner particles adhering triobelectrically thereto. A single component dry developer material typically comprising toner particles only can also be used. The toner image formed by such development is subsequently transferred at a transfer station onto a copy sheet fed to such transfer station, and on which the toner particles image is then heated and permanently fused so as to form a "hardcopy" of the original image.
It is well known to provide a number of the elements and components, of an electrostatographic reproduction machine, in the form of a customer or user replaceable unit CRU. Typically such units are each formed as a cartridge that can be inserted or removed from the machine frame by a customer or user. Reproduction machines such as copiers and printers ordinarily include consumable materials such as toner, volume limiting components such as a waste toner container, and life cycle limiting components such as a photoreceptor and a cleaning device. Because these elements of the copying machine or printer must be replaced frequently, they are more likely to be incorporated into a replaceable cartridge as above.
There are therefore various types and sizes of cartridges, varying from single machine element cartridges such as a toner cartridge, to all-in-one electrostatographic toner image forming and transfer process cartridges. The design, particularly of an all-in-one cartridge can be very costly and complicated by a need to optimize the life cycles of different elements, as well as to integrate all the included elements, while not undermining the image quality.
The electrostatographic printing process includes six steps or stations within the printing machine. The first of these steps is the charging step performed at the charging station. The second of these steps is the imaging step performed at the imaging station. The third step is the development step performed at the development station. The fourth step is the transfer step occurring at the transfer station. The fifth step is the fusing step occurring at the fusing station. The sixth step is the cleaning step performed at the cleaning station.
A typical prior art electrostatographic printing machine is shown in FIG. 2 as printing machine 1. The printing machine 1 includes a photoconductive surface in the form as shown as photoconductive drum 2. While the printing machine 1 as shown in FIG. 2 is in the form of a drum, prior art printing machines also include a flexible belt which are supported by rollers (not shown).
The printing machine 1 includes a charging station A at which a latent image is applied to the photoconductive drum 2. The charging station A includes a charge corotron 3 for generating ions to charge the drum 2. The charge corotron 3 may be any corotron capable of applying a charge to the drum 2. For example, the charge corotron 3 may include a wire type corotron.
The printing machine 1 further includes an imaging station B at which an image is formed by exposing light to a portion of the latent image is formed by the charging station A. The imaging station B may be in the form of a light lens imaging station or a raster optical scanner laser type of image station.
The printing machine 1 further includes a development station C where marking particles are utilized to develop the latent image formed by the imaging station B. The development station C may include for example a roller 4 for advancing the marking particles toward the drum 2.
The printing machine 1 further includes a transfer station D at which the developed image from the development station C is transferred to a sheet.
The printing machine 1 further includes a fusing station E at which the developed image is fused to the sheet by fusing rollers 5.
The printing machine 1 further includes a cleaning station F at which the photoconductive drum 2 is cleaned of contamination and residual particles so that the printing machine 1 may be recharged at charging station A. Cleaning station F may, for example, include a detoning roll, a rotating brush or as shown in FIG. 2, include a cleaning blade 6 for removal of the contamination and residual toner particles on the photoconductive drum 2.
An alternative form of a prior art machine as shown as printing machine 1' as shown in FIG. 3. The printing machine 1' includes a photoconductive surface in the form of the photoconductive drum 2. The photoconductive surface may alternatively be in the form of a belt supported by rollers (not shown). The printing machine 1' includes a charging station A' at which a charge is applied to the photoconductive drum 2. For example, the charging station A' may include a biased charge roller 7 which applies the charge to the photoconductive drum 2.
After the photoconductive surface has been charged, the photoconductive surface is exposed at imaging station B'. At imaging station B', the charge surface is exposed to form a latent image. The exposure station may include a light lens system or a raster output scanner laser system.
At development station C', the latent image is developed with marking particles to form the developed image. The marking particles are advanced toward the photoconductive drum 2 by for example a developer roller 8.
At transfer station D', the developed image from the development station C' is transferred to a sheet.
At fusing station E', a set of fusing rolls 9 is utilized to fuse the developed image onto the sheet.
At cleaning station F', the cleaning blade 6 is utilized to remove the excess marking particles and contamination from the photoconductive drum 2 so that the xerographic process can begin anew at charging station A'.
Prior art printing machines such as printing machine 1 of FIG. 2 and printing machine 1' of FIG. 3 require separated apparatus for the charging station and for the cleaning station. The charging station and the cleaning station require expensive hardware as well as significant assembly time and cost. Further, the requirement for separate cleaning and charging systems represents an increase in the development time to develop a xerographic system that will properly operate in the printing machine. Further, the requirement for separate cleaning and charging station results in a large, cumbersome xerographic system. Component size and gravity considerations limit the design flexibility for the printing machine with separate cleaning and charging stations. Further, the cleaning and charging systems each require physical space about the photoconductive surface requiring the xerographic system to become large.
Prior art charging devices are particularly wrought with problems. For example, corotron type of charging devices as shown in FIG. 2 are a significant source of ozone. Attempts have been made to reduce the ozone generated from corotron devices. For example, carbon paper lining may be added to the shield about the corotron or a deep AG coating may be applied to the corotron grid. The carbon paper lining and AG coating serve to reduce the ozone generated in the corotron device. Even with the attempts to reduce the ozone of the corotron, corotrons tend to be a significant source of ozone emission.
The alternate type of charging device is in the form of a bias charge roller. A bias charge roller contacts the photoreceptor and can cause wear to the photoconductive surface.
The following disclosures may be relevant to various aspects of the present invention:
U.S. Pat. No. 5,166,733 Patentee: Eliason Issue Date: Nov. 24, 1992 PA1 U.S. Pat. No. 5,085,171 Patentee: Aulick, et al. Issue Date: Feb. 4, 1992 PA1 U.S. Pat. No. 4,935,784 Patentee: Shigehiro, et al. Issue Date: Jun. 19, 1990 PA1 U.S. Pat. No. 4,901,116 Patentee: Haneda, et al. Issue Date: Feb. 13, 1990 PA1 U.S. Pat. No. 4,777,904 Patentee: Gundlach, et al. Issue Date: Oct. 18, 1988 PA1 U.S. Pat. No. 4,637,340 Patentee: Thompson, et al. Issue Date: Jan. 20, 1987 PA1 U.S. Pat. No. 4,523,833 Patentee: Jones Issue Date: Jan. 18, 1985 PA1 U.S. Pat. No. 4,348,979 Patentee: Daintrey Issue Date: Sep. 14, 1982 PA1 U.S. Pat. No. 43,660,863 Patentee: Gerbasi Issue Date: May 9, 1972 PA1 U.S. patent application Ser. No. 08/970,313 Applicants: Kumar, et al. Filing Date: Nov. 14, 1997
U.S. Pat. No. 5,166,733 discloses an electrophotographic printer having a photoreceptor surface for the creation of electrostatic latent images thereon and a rotating roll for conveying toner particles to a development zone adjacent the photoreceptor surface, an apparatus prevents the migration of toner particles from the roll. A blade, in contact with the roll adjacent one end thereof, causes toner particles adhering to an area of the roll to be moved toward the roll center as the roll rotates.
U.S. Pat. No. 5,085,171 discloses a doctor blade having an outer metal surface on a grit layer with flexible backing. The blade is pushed by foam or, alternately by inherent resilience, onto a developer roller. The compliance reduces toner variations which result from surface variations of the blade and the roller.
U.S. Pat. No. 4,935,784 discloses an apparatus for developing a latent image on a photo-sensitive drum which apparatus uses as a developing agent microcapsule toner magnetic particles wherein regulation member contacts the surface of developing agent carrier, or sleeve, under pressure for regulating the thickness of a uniform thin layer of the particles deposited on the sleeve and the contact pressure of the regulation member on the sleeve is not more than 20 g/cm. Preferably, the toner particles have a residual magnetic level not more than 4 emu/g and a magnetic holding force not more than 90 Oe.
U.S. Pat. No. 4,901,116 discloses an electrostatic copier having a smoothing member at an upstream side in the developer conveying direction in the vicinity of a developing area between a developer conveyer and an image-forming member in order to smooth a developer layer on the conveyor prior to transfer of the image forming member. Further, one surface of the smoothing member is so arranged as to come in contact with the image-forming member and another surface smoothes the developer layer. The developer conveyer has a magnet member therein and the magnet member is positioned to face the smoothing portion of the smoothing member.
U.S. Pat. No. 4,777,904 discloses a touchdown development system includes a donor roll positioned closely adjacent a photosensitive member in order to develop an image on the surface of the photosensitive member. A reverse mounted doctor blade is employed in the system along with a toner pump in order to apply a smooth and uniform layer of toner onto the surface of the donor roll.
U.S. Pat. No. 4,637,340 discloses a structure for metering the developer to a uniform thickness on a developer roll. To this end a magnetic steel shim or blade member is provided in the vicinity of a magnetic developer roll. The shape and location of the shim or blade member in the developer sump is such that a transport magnet (i.e. developer roll) rotatably supported adjacent the outlet of the sump causes vibration of the shim or blade due to the coupling and decoupling therebetween of the magnetic force fields created through the rotation of the developer roll. The developer which passes between the shim or blade member and the developer roll is freed of agglomerations and is metered to a predetermined thickness on the developer roll.
U.S. Pat. No. 4,558,943 discloses an apparatus in which a latent image recorded on an image receiving member is developed. A developer roller transports the marking particles into the development zone. The developer roller has the exterior surface thereof roughened forming a multiplicity of peaks extending outwardly therefrom with a coating of polymeric material filling the space between adjacent peaks. A blade is positioned to have the free end thereof contacting the peaks on the developer roller. The blade has a plurality of apertures therein through which the marking particles pass. In this way, the thickness of the layer of marking particles on the developer roller is controlled.
U.S. Pat. No. 4,523,833 discloses an apparatus in which a latent image recorded on an image receiving member is developed. A developer roller transports marking particles into the development zone. A blade having at least one aperture therein through which the marking particles pass has the free end portion thereof contacting the developer roller. A controller regulates the quantity of marking particles passing through the aperture in the blade. In this way, the thickness of the layer of marking particles on the developer roller is adjusted.
U.S. Pat. No. 4,348,979 discloses a magnetic brush monocomponent developer unit includes a doctor blade for rendering uniform the layer of toner magnetically attracted to the surface of a shell within which a rotating magnetic roller is positioned. A coil connected to the doctor blade receives an alternating magnetic field in response to rotation of the roller and the induced voltage fluctuations in that coil are sensed to determine when the voltage amplitude exceeds a given threshold value (indicative of a low amount of toner held back by the doctor blade) at which application of toner to the layer by way of a metering roller and sealing brushes is resumed.
U.S. Pat. No. 3,660,863 discloses an elastomeric blade for removing a dry particulate material from a surface to which the particulate material is electrostatically bonded. An edge of the blade is supported in pressure contact against the surface in a cutting tool fashion and relative motion between the blade and the surface produced wherein the edge of the blade moves between the particulate material and the surface to cut or chisel the material from the surface.
U.S. Pat. No. 4,523,833 discloses a process cartridge for use in a printing machine. The process cartridge includes a housing having a first support surface and a second support surface. The housing further includes a first member rotatably secured to the housing at the first support surface and the second support surface. The housing further includes a second member spaced from the first member and rotatably secured to the housing at the first support surface and the second support surface. The housing further includes a first gear operably associated with the first member and rotatable therewith. The housing further includes a second gear operably associated with the second member and rotatable therewith. The first gear and the second gear are positioned adjacent the first support surface.